E-R模型是用E-R图来描述现实世界的概念模型。E-R图的组成 元素有____

A. SELECT stu_name, COUNT(stu_sex) FROM student GROUP BY stu_sex;

B. SELECT stu_sex, COUNT(stu_sex) FROM student GROUP BY stu_sex;

C. SELECT stu_name FROM student GROUP BY stu_sex;

D. SELECT stu_sex, COUNT(stu_name) FROM student GROUP BY stu_name;

A. SELECT stu_id FROM student group by stu_id where AVG(score) >=60

B. SELECT stu_id FROM student group by stu_id having AVG(score) >=60

C. SELECT stu_id FROM student where AVG(score) >=60

D. SELECT stu_id FROM student having AVG(score) >=60

A. 数据谁使用、安 全谁负责、责任 谁承担

B. 最小化授权

C. 没有明确要求

D. 数据申请得越多 越好

A. 圆形

B. 矩形

C. 椭圆形

D. 菱形

A. 数据探查

B. 特征工程

C. 数据建模

D. 模型验证